Patent Document 1 discloses a structure shown in FIG. 24 as an example of a text mining device. This conventional text mining device includes a basic dictionary storage section, a document data storage section, a field dependent dictionary storage section, a language characteristics analysis device, a language analysis device, a pattern extraction device, and a frequent pattern display device.
The text mining device in FIG. 24 generally operates as follows. Firstly, the language characteristics analysis device creates a field dependent dictionary based on a basic dictionary and document data. Next, the language analysis device creates sentence structures, such as syntax trees at each sentence based on the basic dictionary, the field dependent dictionary, and the document data, where the sentence structure means a graph structure expressing a text obtained by parsing of the text. Next, the pattern extraction device extracts a characteristic structure using the sentence structures, and stores a sentence matching the characteristic structure of the document data in a frequent pattern matching document storage section, at the same time, outputs the characteristic structure, where the characteristic structure means a partial structure characterizing a text collection such as a frequent pattern which is extracted by application of the text mining processing to a partial structure of the sentence structure.    Patent Document 1: JP2001-84250